During 1975-76, we plan to extend our laser Doppler studies of very low density serum lipoproteins to include a variety of abnormal lipoproteins obtained from patients with various lipid transport diseases. Moreover, we believe that we can directly characterize the particle sizes by studies on unfractionated sera obtained directly from the patient without further purification. Thus, we hope to take advantage of the fact that the laser Doppler technique yields a high order average radius (equals negative sigma Cir 6 sub 1/negative sigma Cir 5 sub 1) which should be characteristic of the largest particles in the serum. We also plan a detailed investigation of the shape of the correlation function obtained by laser Doppler scattering to yield a heterogeneity index characteristic of the distribution of particle sizes in a sample. We will also measure the angular dependence of the Doppler scattering and the angular dependence of the scattering intensity. It should be possible to combine all these data to develop a meaningful description of the sizes of lipoproteins in the sera of each patient. This information obtained by the laser Doppler technique will be correlated with that obtained from flotation distributions in the ultracentrifuge and from electron microscope particle counts. Together these studies should yield a meaningful physical description of VLDL sizes and densities in healthy persons and patients with lipid transport diseases.